\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,xscale=0.6]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw [->](-2,0)--(10,0)node[right]{$\omega t$};
  \draw [->](0,-1.5)--(0,1.5)node[right]{$i$};
  \draw [ultra thick] plot[domain=0:9, samples=1000] function{-cos(x+.7)*.7} node [above]{$i_2$};
  \draw [ultra thick] plot[domain=0:8.5, samples=1000] function{sin(x+1)} node [below]{$i_1$};
  \draw [ultra thick, dashed] plot[domain=-1:0, samples=100] function{-cos(x+.7)*.7};
  \draw [ultra thick, dashed] plot[domain=-1:0, samples=100] function{sin(x+1)};
  \node at (-.25,-.25){$O$};
  \draw [dashed] (-1,0)--(-1,-1.5);
  \draw [dashed] (3.1416/2-.7,0)--(3.1416/2-.7,-1.5);
  \draw [<->] (0,-1)--node[below]{$\phi_1$}(-1, -1);
  \draw [<->] (0,-1)--node[below]{$\phi_2$}(3.1416/2-.7,-1);
\end{tikzpicture}
\end{document}